Hi
Let’s back off a bit here.
If the chimney is above the rest of the house, simply putting the antenna a foot or
two above the chimney will get you past the immediate issues of the house blocking
or reflecting stuff.
If the top of the chimney has a view to the south down to about 10 degrees off the
horizon *and* it maintains that for most of a +/- 100 degree arc, that is doing fine.
If the application is just timing, having a mount that does not move around a lot
is a really good idea.
With any antenna, putting it up higher than needed simply makes it a better lightning
target (you *will* have proper grounding and suppression on this antenna, it still
is not perfect).
On a GPSDO with a good sky view, you may well set the elevation mask to something
like 20 or even 30 degrees to improve the timing performance. When you do, all
the effort to get a sky view down to 10 degrees becomes a bit less worthwhile.
=====
So: what is the reason for getting the antenna 15 feet above the chimney?
Bob
> On Feb 18, 2017, at 12:57 AM, timenut at metachaos.net wrote:
>> I have finally ordered a GPSDO (probably get here in April). In the meantime,
> I have the GPS antenna (Luctel, 26Db). I picked up a 20' solid section of 1 1/4"
> copper pipe at the plumbing store with the intention of mounting it to my
> chimney.
>> My question is about the stability of that mounting. I expect that 16 or 17
> feet of the pipe will be above the chimney. The weight of the GPS antenna is
> trivial. The effective cross section area of the pipe is very small as well,
> so I would think that wind effects would be pretty small even for a good
> breeze.
>> Will that be sufficiently stable, or will I need to include guy wires? If so,
> are there any recommendations in that area. I don't really have any experience
> putting up antennas. I know that TV antennas are much heavier and, even though
> not mounted as high, still 10' or so is common without guy wires.
>> Thanks.
>> Michael
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